A recent Clinical Vistas article1 provides an interesting look at the similarity between homogentisic acid, which is excreted in the urine of people with alkaptonuria, and hydroquinone, which is used in the process to develop photographs. Unfortunately, both of the chemical structures provided in the article are wrong. Homogentisic acid and hydroquinone are both aromatic compounds (the author alludes to this by referring to the benzene ring of hydroquinone) that have a 6-membered, not an 8-membered, ring.

Perhaps a minor point, but worth correcting, because in chemistry, biochemistry and the medical arts and sciences, structure is everything.